Data Link Layer

The data link layer transforms the physical layer a a raw transmission facility to a reliable link and is resposible for nod eto node delivery. It makes the physical layer error free for the network layer.
This layer includes the following responsibilities :

• It divides the stream of bits received from network layer into manageable data units called frames.
• If frames are to be distributed to different systems on network, it adds a header to the frame to define the physical address of the sender(source address) and/or receiver(destination address) of frame.
• It also control that the data rate absorbed by reveiver must match the data rate at which is sent by sender called flow control.
• It also control the retransmitting of data if any frame is lost or damaged and the duplication of frames called error control.
• If two or more devices are connected to a same link. Then data link layer determines that which device has control over the link at any given time.